1. Field of the Invention
The invention relates to a pipe-shaped socket to be connected to an opening of a container comprised primarily of thermoplastic material, in particular, polyethylene. The pipe-shaped socket comprises a tubular first part, which is comprised primarily of a thermoplastic material which has at most a slight swelling capacity, and further comprised of an annular second part of primarily thermoplastic material which has a greater swelling capacity than the first plastic material. The annular second part with the first rim having a smaller diameter is connected in a material-bonding and positive-locking way to the first part between two outer ribs surrounding the first part by injection molding one of the first and second parts about the other one of the first and second parts and is to be fastened with the second rim having the larger diameter to the edge of the opening of the container by material bonding.
2. Description of the Related Art
Devices of the aforementioned kind are known, for example, from German patent application No. 195 33 920 A1. The socket described therein has an annular second part of a substantially S-shaped stepped cross-section with a radially inwardly projecting flange projecting between the outer ribs of the first part and a radially outwardly projecting second flange. The container opening has a diameter which widens from the interior to the exterior in a stepped fashion so that an annular flange results which projects radially inwardly within the container opening at the inner side of the container. The second radial outer flange of the annular second part is fastened by material bonding onto this annular flange. The type of material bonding is not disclosed. If they were to be fused by applying heat, an axial pressure would have to be applied onto the radial surfaces of the second annular flange and the flange in the opening contacting one another. This would entail the risk that the flange in the opening and also the second flange of the ring would bend. An adhesive connection would require a material-intensive and labor-intensive application of an adhesive or bonding agent. When the container contains fuels such as gasoline or diesel fuel, there is the risk that the annular second part will swell when the exposed part of its inner side comes into contact with the fuel. This entails the risk that the outer rib of the first part resting against the inner side of the annular second part would tear and that, moreover, the fuel would penetrate between the radially inner first flange of the ring and the axially inner rib of the tubular first part and that the swelling would continue directly to the tubular first part so that the connection between the first and second parts finally would dissolve or at least begin to leak so that fuel can flow from the container.
It is an object of the present invention to provide a pipe-shaped socket of the aforementioned kind in which the connection of the two parts can withstand swelling of the plastic material of the second part upon contact with a liquid which will cause it to swell, in particular, fuels such as gasoline or diesel fuel, and the connection between the second part and the container can be produced reliably as a fused or welded connection.
In accordance with the present invention, this is achieved in that the second part is substantially bell-shaped and the outer rib positioned between its rims comprises a circumferential flexible lip welded to the inner side of the second part, the lip extending to the second rim of the second part so that the majority of the inner side of the second part is covered by the first part.
In this embodiment of the two parts, the lip which forms an extension of the axially inwardly positioned outer rib of the first part first protects additionally a large portion of the inner side of the second part against contact with the fuel contained in the container. The lip leaves a small portion of the inner side of the second part exposed so that the second part upon contact with a liquid, such as fuel, can still swell. The swelling, however, would take place primarily in the direction toward the substantially freely exposed outer side of the second part without this posing the risk of tearing within the second part. Since the lip is flexible, it can also yield to a swelling toward the inner side of the second part without tearing. The fuel therefore cannot penetrate farther between the outer ribs, as would be the case for a tear in the inner rib. Between the end face of the rim of the annular second part having the larger diameter and the outer side of the edge area of the opening in the container, a welding or fusing connection can be simply provided, for example, by butt-welding, wherein the end face of the rim having the larger diameter is pressed against the outer side of the container, without the container edge deforming, because a shoulder of the diameter of the container edge and thus of the radially inner, thinner flange of the container edge on which the rim of the annular second part would be seated can be eliminated as a result of the second part radially widening in the direction of the container. Not to cover a small portion of the inner side of the second part by the lip has the advantage that the welding bead, resulting when producing the welding connection by pressing the rim of the second part having the larger diameter against the outer side of the container, can expand unimpededly.
Preferably, the inner side of the first rim of the second part is provided with radial projections which engage the material of the first part between the outer ribs. This results in an additional positive-locking rotational securing action between the two parts so that the connection between the two parts withstands a torsional force which, when exerting an accidental torque about the longitudinal center axis of the tubular first part, is greater between the two parts than between the second part and the container.
It is furthermore beneficial when the projections on the second part extend axially and when their radial (transverse) section as well as their axial section has a substantially trapezoidal contour. This shape ensures that upon injection molding around the rim of the annular second part having the smaller diameter, the material of the first part will tightly flow about the projections without forming bubbles during molding of the first part in the mold.
Moreover, the first rim of the second part can have a radially inwardly descending slanted portion. This slanted portion ensures that the pressure of the material of the first part which is injected axially against the slanted portion into the mold provides a radial component which presses the second part securely against the inner side of the mold so that the second part is less easily deformed in the axial direction during injection molding of the first part.